cis,cis,cis‐Tetra­methyl 1,2,4,5‐cyclo­hexane­tetra­carboxyl­ate

The title compound, C₁₄H₂₀O₈, was synthesized from the hydrogenation of tetra­methyl 1,4‐cyclo­hexa­diene‐1,2,4,5‐tetra­carboxyl­ate with a catalytic amount of palladium/carbon. All four carbonyl moieties of the methyl ester groups are on the same face of the chair‐conformed ring. The substantial ring distortion associated with the 1,3‐diaxial methoxycarbonyl substituents is reflected in the large difference between bond angles as well as torsion angles, respectively, that in undistorted cyclo­hexanes would be approximately the same.     

Generalized nonlinear Schrödinger equation with time-dependent dissipation

The generalized nonlinear Schrödinger equation with time-dependent dissipation [1] is considered using decomposition [2].     

Deep penetration of a PDT drug into tumors by noncovalent drug-gold nanoparticle conjugates

Efficient drug delivery to tumors is of ever-increasing importance. Single-visit diagnosis and treatment sessions are the goal of future theranostics. In this work, a noncovalent PDT cancer drug-gold nanoparticle (Au NP) conjugate system performed a rapid drug release and deep penetration of the drug into tumors within hours. The drug delivery mechanism of the PDT drug through Au NPs into tumors by passive accumulation was investigated via fluorescence imaging, elemental analysis, and histological staining. The pharmacokinetics of the conjugates over a 7-day test period showed rapid drug excretion, as monitored via the fluorescence of the drug in urine. Moreover, the biodistribution of Au NPs in this study period indicated clearance of the NPs from the mice. This study suggests that noncovalent delivery via Au NPs provides an attractive approach for cancer drugs to penetrate deep into the center of tumors.     

Ammonium octahydrotriborate (NH4B3H8): new synthesis, structure, and hydrolytic hydrogen release

A metathesis reaction between unsolvated NaB(3)H(8) and NH(4)Cl provides a simple and high-yield synthesis of NH(4)B(3)H(8). Structure determination through X-ray single crystal diffraction analysis reveals weak N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8) and strong N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8)·18-crown-6·THF adduct. Pyrolysis of NH(4)B(3)H(8) leads to the formation of hydrogen gas with appreciable amounts of other volatile boranes below 160 °C. Hydrolysis experiments show that upon addition of catalysts, NH(4)B(3)H(8) releases up to 7.5 materials wt % hydrogen.     

Bending of an elastoplastic strip with isotropic and kinematic hardening

Summary  We propose an exact analysis for finite bending of a compressible elastoplastic strip with combined hardening at a given stretch normal to the bending plane. We apply the self-consistent eulerian rate-type elastoplastic model based on the logarithmic rate, in conjunction with a Tresca-type loading function. Utilizing the maximum circumferential stretch at the outer surface as an independent parameter, we derive exact analytic expressions for the bending angle, the bending moment, the outer and inner radii, the radii of the two elastic-plastic interfaces and the circumferential stretches at these two interfaces, as well as the stress distributions in every current cross section. In particular, we establish an explicit relation between the two circumferential stretches at the two elastic-plastic interfaces, and we show that this relation is universal for all cases of hardening. We show also that the maximum and minimum circumferential stretches at the outer and inner surfaces obey a reciprocal relation in the course of both elastic and elastic-plastic deformations. Received 4 June 2002; accepted for publication 14 November 2002 This research was carried out under financial support from the German Science Foundation (DFG) (Contract No.: Br. 580/26-2) and from Alexander von Humboldt Foundation. We wish to express our sincere gratitude to these Foundations.